A recent study by the Centers for Disease Control and Prevention found that 80% of Americans 16 and older have at least some immunity to COVID-19 and that prior infection provides similar immunity as vaccination.

The study, led by the CDC's Dr. Jefferson Jones, aimed to see how close the United States might be to herd immunity, though it did not claim to be close to knowing yet, CNN reported.

The team worked with blood collection organizations in every state as well as Washington, D.C., and Puerto Rico, testing the blood of 74% of the population.

In July 2020, 3.5% of samples carried antibodies to the virus that causes COVID-19. The number increased to 11.5% by December. With no vaccine available, all those antibodies were from infections.

By May 2021, the number had risen to 83.3%. Most of those were from vaccinated people.

Those numbers predate the delta variant, the researchers noted. They also said they didn't measure other factors, such as T-cells, and one that might cause broader immunity.

"Several large studies have shown that among individuals who are seropositive from prior SARS-CoV-2 infection, COVID-19 incidence is reduced by 80% to 95%, similar to vaccine efficacy estimates," they said.

"The study will continue until at least December 2021, and results will be made available on the CDC's website," they wrote.

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